Biomedical electrode

ABSTRACT

A biomedical electrode including a flexible pad having a top surface and a bottom surface; an asymmetrical, linearly aligned array of signal contacts retained by the flexible pad and each having a contact surface projecting from the bottom surface and a coupling surface projecting above the top surface; and a connector including a plurality of connector contacts each being shaped and arranged for electrical connection to a different one of the coupling surfaces. The asymmetrical array of signal contacts facilitates proper positioning of the electrode on the skin.

This application is a Divisional of application Ser. No. 09/192,949filed on Nov. 16, 1998 Now U.S. Pat. No. 6,129,666.

BACKGROUND OF THE INVENTION

This invention relates generally to a biomedical electrode and, moreparticularly, to a disposable biomedical electrode for establishingelectrical contact between a skin portion of the human anatomy andelectrical diagnostic equipment.

Many types of disposable biomedical electrodes are known. Typically theycomprise an electrically-conductive terminal member having means forelectrical connection to electromedical equipment, an adhesive tape orpad for holding the terminal member in place on the skin; and anelectrically-conductive, conformable interfacing material such as anelectrolyte gel or paste over the surface of the terminal member whichcontacts the skin to reduce skin impedance and improve electricalcontact between the skin and the terminal member. Although priorelectrodes function in many applications, they suffer a variety ofindividual and collective deficiencies such as being difficult toproperly orient on the body and failing to provide signals withconsistent, repeatable amplitude and frequency parameters.

SUMMARY OF THE INVENTION

The invention is a biomedical electrode including a flexible pad havinga top surface and a bottom surface; an asymmetrical, linearly alignedarray of signal contacts retained by the flexible pad and each having acontact surface projecting from the bottom surface and a couplingsurface projecting above the top surface; and a connector including aplurality of connector contacts each being shaped and arranged forelectrical connection to a different one of the coupling surfaces. Theasymmetrical array of signal contacts facilitates proper positioning ofthe electrode on the skin.

According to one feature of the invention, the connector furthercomprises a substrate retaining the connector contacts in anasymmetrical, linearly aligned array geometrically matching the array ofsignal contacts. The matching arrays facilitate interconnection of theconnector contacts and coupling surfaces.

According to other features of the invention, the substrate is a caseretaining an amplifier interconnected with the connector contacts, eachof the coupling surfaces is defined by a snap contact, each of theconnector contacts is a receptacle for receiving one of the snapcontacts, and each of the signal contact surfaces is formed by a gelsubstance. These features provide an efficient, easily employedelectrode system.

According to yet another feature of the invention, the bottom surface ofthe pad is adhesive to facilitate attachment of the electrode to theskin.

According to an additional feature, the electrode includes indiciadisposed on the pad and indicating, with respect to an adjacent bundleof muscle fibers, a desired linearly directed orientation for the arrayof signal contacts.

According to a further feature, the electrode includes indicia disposedon the substrate and indicating, with respect to an adjacent bundle ofmuscle fibers, a desired linearly directed orientation for said array ofconnector contacts.

According to other features of the invention, the indicia comprisesdirectional indicators disposed, respectively, on the top surface andthe substrate.

According to an additional feature of the invention, the flexible padincludes first and second portions divided by perforations adapted tofacilitate separation thereof. The first and second portions can beselectively separated to reduce the size of the electrode for certainapplications.

According to still other features of the invention, the first portion isa central portion and retains the signal contacts and the second portionis a marginal portion surrounding the central portion. With thisarrangement, the separated central portion functions as a completeelectrode.

According to another feature of the invention, the contact surfaces haveareas of different size. This feature facilitates the formation ofcontact surfaces which exhibit desirable equal current density.

According to features of another embodiment, a biomedical electrodeincludes a flexible pad with adhesive top and bottom surfaces and alinear array of slots, a conductive gel contact retained in each slotand having a contact surface forming a portion of the bottom surface anda coupling surface forming a portion of the top surface, and a connectorwith connector contacts arranged to engage the coupling surfaces. Theadhesive surfaces facilitate assembly of the pad between the connectorand a muscle to be monitored.

According to features of yet another embodiment, a biomedical electrodeconsists of a flexible connector having an adhesive substrate; aplurality of connector contacts projecting from the substrate, eachcontact formed by a plurality of conductive bristles; and a flexibleamplifier retained by the connector and interconnected with thecontacts. The flexible connector can be positioned directly on skincovering a muscle to be monitored and the conductive bristles projectthrough hair to insure good electrical contact.

DESCRIPTION OF THE DRAWINGS

These and other objects and features of the invention will become moreapparent upon a perusal of the following description taken inconjunction with the accompanying drawings wherein:

FIG. 1 is an elevational view of a biomedical electrode according to theinvention;

FIG. 2 is a top view of a pad component of the electrode shown in FIG.1;

FIG. 3 is a bottom view of the pad shown in FIG. 2;

FIG. 4 is a top view of a connector component of the electrode shown inFIG. 1;

FIG. 5 is a bottom view of the connector shown in FIG. 4;

FIG. 6 is a schematic top view of the electrode of FIG. 1 mountedadjacent to a bundle of muscle fibers;

FIG. 7 is a side view of the electrode and muscle fiber bundle shown inFIG. 6;

FIG. 8 is a plan view of another pad embodiment of the invention;

FIG. 9 is a side elevational view of the pad shown in FIG. 8;

FIG. 10 is a plan view of a connector for use with the pad illustratedin FIGS. 8 and 9;

FIG. 11 is a perspective view of a contact used with the connector ofFIG. 10;

FIG. 12 is a plan view of another biomedical electrode embodiment of theinvention;

FIG. 13 is a perspective view of a contact used with the electrode ofFIG. 12;

FIG. 14 is a perspective view of another biomedical electrode;

FIG. 15 is a partial side view of the electrode shown in FIG. 14;

FIG. 16 is a perspective view of another biomedical electrodeembodiment;

FIG. 17 is an end view of the electrode shown in FIG. 16;

FIG. 18 is an exploded perspective view of another biomedical electrodeembodiment;

FIG. 19 is a top view of a modified adhesive interface for the electrodeembodiment shown in FIG. 18; and

FIG. 20 is a partial cross-section of the interface shown in FIG. 19.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A biomedical electrode 11 includes a connector 12 and a flexible foampad 13 illustrated in FIG. 1. As shown in FIGS. 2 and 3, the pad 13retains an asymmetrical, linearly aligned array of signal contacts 16.Each of the signal contacts 16 has a button snap portion forming acoupling surface 17 that projects above a top surface 18 of the pad 13.Projecting from a bottom surface 21 of the pad 13 are contact surfaces22 of the signal contacts 16. Each of the contact surfaces 22 is formedwith a suitable, electrically conductive gel material and the bottomsurface 21 is provided with suitable adhesiveness. Included among thesignal contacts 16 are a pair of detection contacts 25, 26 (FIG. 3)which have contact surfaces of equal area and a reference contact 27which has a contact surface area substantially equal to the sum of theareas of the contact surfaces of the detection contacts 25, 26.Asymmetry for the array of signal contacts 16 is established byproviding a larger spacing between the reference contact 27 and thedetector contact 25 than between the detector contacts 25, 26.

A first central portion 31 of the pad 13 is divided from a secondmarginal portion 32 thereof by annular perforations 35. An additionalline of perforations 36 extend between the annular perforations 35 andan outer edge of the pad 13. The perforations 35, 36 facilitate tearingof the pad 13 to separate the first and second portions 31, 32 thereof.As shown in FIGS. 2 and 3, all of the signal contacts 16 are retained bythe first central portion 31 of the pad 13. Disposed on the top surface18 of the pad 13 is indicia 38 in the form of an arrow 39 aligned withthe linear array of signal contacts 16 and pointed from the referencecontact 27 toward the detection contacts 25, 26.

The connector 12 (FIGS. 4 and 5) includes a molded case 41 that retainsa preamplifier 42. Disposed on a bottom substrate surface 44 of the case41 is an asymmetrical, linearly aligned array of connector contacts 45interconnected with the preamplifier 42. Included among the connectorcontacts 45 are a reference connector contact 46 and a pair of detectorconnector contacts 47, 48. Each of the connector contacts 45 is acylindrical receptacle shaped for press fitted engagement with one ofthe signal contact coupling surfaces 17 on the top surface 18 of the pad13. The array of connector contacts 45 geometrically match the array ofsignal contacts 16 so as to facilitate interconnection thereof.Extending from the molded case 41 is an electrical cable 49interconnected with the preamplifier 42 and the connector contacts 45.Connector indicia 51 in the form of an arrow 52 is disposed on a topsurface 53 of the connector case 41. The arrow 52 is aligned with thelinear array of connector contacts 45 and points in a direction from thereference connector contact 46 toward the detector connector contacts47, 48.

Prior to use of the electrode 11, the connector 12 is attached to thepad 13 by press fitting the button snaps 17 into the connector contactreceptacles 45. Next, the adhesive bottom surface 21 of the pad 13 isadhered to the skin of a test subject adjacent to a bundle 54 of musclefibers 55 as shown in FIGS. 6 and 7. Alternatively, the pad 13 first canbe fixed on a test subject and then attached to the connector 12. Propermating of the connector contacts 45 and signal contacts 16 is insured bythe asymmetry of the contact arrays. Either one or both of the arrows38, 52 is used to properly orient the electrode 11 with respect to themuscle fibers 55. Proper orientation aligns the arrows 39, 52 with thefibers 55 of the bundle 54 and pointed in a direction from a proximalend 57 toward a distal end 58 of the bundle 55. The proximal end 57 islocated adjacent to an innervation zone 60 established at a terminalportion of a nerve 59. That arrangement of the electrode 11 establishesa known positive potential for the detector contact 25 and a negativepotential for the detector contact 26.

Illustrated in FIGS. 8-11 is another biomedical electrode consisting ofa flexible pad 61 shown in FIGS. 8 and 9 and a connector 62 shown inFIGS. 10 and 11. The pad 61 has a top surface 63 with a portion coveredby an adhesive layer 64 and a bottom surface 65 with a portion coveredby an adhesive layer 66. Extending through the pad 61 are three linearlyarranged, parallel slots 71-73 with elongated rectangularcross-sections. Each of the slots 71-7 is filled with a conductive gelthat forms, respectively, a reference signal contact 75 and a pair ofdetection signal contacts 76, 77. Provided by the signal contacts 75-77are, respectively, elongated coupling surfaces 81-83 which form portionsof the top surface 63 project above and transversely beyond top edges ofthe slots 71-73. Also provided by the signal contacts 75-77 are,respectively, elongated contact surfaces 85-87 that form portions of thebottom surface 65 and are aligned with the adhesive layer 66. As in theelectrode embodiment 11, the contact surface 85 has an areasubstantially equal to the sum of the areas of the contact surfaces 86and 87.

A tab 91 is attached to one end 92 of the top surface. Retained by theupper surface of the tab 91 is alignment indicia in the form of a line93 having a pre-determined shape. The function of the indicia 93 isdescribed below. Also retained by the tab 91 is instructional textexplaining proper use of the electrode 61.

The connector portion 62 of the electrode consists of a molded case 95with a bottom surface 90 supporting a linear array of connector contactsincluding a reference connector contact 96 and a pair of detectorconnector contacts 97. As illustrated in FIG. 11, the detector connectorcontacts 97 are electrically conductive blocks having exposed, elongatedrectangular contact surfaces 98 that align with the detector couplingsurfaces 82, 83 of the pad 61. The reference connector contact 96 alsois a block but with a larger rectangular contact surface 99 that alignswith the reference coupling surface 81 of the pad 61. Retained withinthe case 95 is a flexible preamplifier 101 connecting the referenceconnector contact 96 and the detector contacts 97 to a cable 102connectable to suitable analysis instrumentation (not shown). An end 103of the case 95 opposite the cable 102 has a curved shape geometricallymatched with the alignment line 93 on the pad 61. Depicted on the topsurface 90 is connector indicia in the form of an arrow 105 pointingfrom the reference connector contact 96 toward the detector connectorcontacts 97.

The electrode 61, 62 is used in the same manner as described above forthe electrode 11. During assembly of the pad 61 and connector 62, propermating engagement between the connector contacts 96, 97 and,respectively, the signal coupling surfaces 81-83 is achieved by aligningthe curved end 103 of the connector 62 with the alignment line 93 on thepad 61. Again, either the tab 91 on the pad 61 or the arrow 105 on theconnector 62 can be used to properly orient the electrode 61, 62 withrespect to a bundle of muscle fibers.

Another biomedical electrode embodiment 111 is illustrated in FIG. 12. Aflexible molded case 112 has a bottom surface 113 formed by an adhesivesubstrate. Retained by the case 112 is a linear array of contactsincluding a reference contact 115 and a pair of detector contacts 116.Each of the detector contacts 116 includes a rectangular block 117 asshown in FIG. 13. Outer elongated, planar surfaces 118 of the detectorcontact blocks 116 are orthogonal to the linear array and substantiallyaligned with the bottom substrate surface 113 of the case 112. Alsoincluded in each detector contact 116 are electrically conductivebristles 121 which project from the outer surface 118. The referencecontact 115 also includes electrically conductive bristles 126projecting from an outer elongated block surface 127 aligned with thesubstrate surface 113. However, again the reference surface 127 has anarea substantially equal to the sum of the detector surfaces 118. Thecase 112 retains a flexible preamplifier 122 that is connected betweenthe contacts 115, 116 and a cable 124 for connection to instrumentation(not shown). Imprinted on a top surface of the case 112 is orientationindicia in the form of an arrow 131 pointing from the reference contact115 toward the detector contacts 116.

The electrode embodiment 111 is used in a manner similar to thatdescribed above for the embodiments 11 and 61, 62. However, in this casethe adhesive substrate 113 of the flexible case 112 is adhered directlyin a contoured fit to the skin covering a bundle of muscle fibers 55 asshown in FIGS. 6 and 7. Again, the arrow 131 is used to properly orientthe electrode 111 with respect to the muscle fibers. The conductivebristles 121, 126 of, respectively, the detector contacts 116 and thereference contact 115 penetrate between any existing body hair to insuregood electrical contact with the skin. Accordingly, valid diagnosticsignal information can be derived with the unitary flexible casecomponent 112.

FIGS. 14 and 15 illustrate another biomedical electrode embodiment 121.An injection molded case 122 retains a preamplifier (not shown ) and hasa top surface 123 and a bottom surface 124. Covering the bottom surface124 is a suitable adhesive substance for securing the case to the skinof a test subject. A pair of parallel, elongated contacts 125 have baseportions retained by the case 122 and an outer portion 126 extendingtransversely to the bottom surface 124. Forming each of the contacts 125are a bundle of electrically conductive bristles 127. Outer ends of thebristles 127 define a pair of concave surfaces 128, 129 intersectingalong a longitudinal axis 130 of the contact 125. Each of the surfaces128, 129 extend inwardly from the axis 130 toward the bottom surface124. Preferably, each of the concave surfaces 128, 129 forms a catenarycurve. Connecting the case 122 to a plug 131 is a wiring harness 132.The contoured bristle contacts 125 equalize tension when secured to skinand allow an accumulation of moisture between the bristles 127 therebyreducing impedance and minimizing the effect of changes in contactpressure between the bristles and skin as the electrode 121 is moved.

FIGS. 16 and 17 illustrate another biomedical electrode embodiment 134.An injection molded case 132 retains a preamplifier (not shown) and hasa top surface 136 and a bottom surface 137 covered with a suitableadhesive for securing the case 135 to the skin of a test subject. A pairof elongated and parallel cylindrical contacts 138 are retained by thecase 135 and project outwardly from the bottom surface 137. Each contact138 has an outer surface portion 139 for contacting the skin afterattachment of the electrode 134. Included in the bottom surface 137 is abase portion 141 inwardly displaced from the outer contact surfaceportions 139 and concave transition portions 142 extending between thebase portion 141 and opposite edges of the outer surface portions 139 ofeach contact 138. A wiring harness 132 connects a plug 131 to the case135. Preferably, each of the transition portions 142 forms a catenarycurve to minimize the skin tensioning effect of the protruding contacts138. In addition, the transition portions 142 eliminate between thecontacts 138 and the skin any cavities which can accumulate sweat andthereby reduce the period in which adhesion to the skin can bemaintained.

Illustrated in FIG. 18 is another biomedical electrode embodiment 145. Amolded case 146 retains a pre-amplifier (not shown) and has a topsurface 148 and a bottom surface 149. Retained by the case are a pair ofelongated, parallel and cylindrical contacts 151 projecting outwardlyfrom the bottom surface 149. A wiring harness 132 connects the case 146to a plug 131. Defined by the bottom surface 149 are a plurality ofrecess grooves 153 extending parallel to the contacts 151 and betweenopposite positions at the perimeter 154 of the bottom surface 149.

Also included in the electrode embodiment 145 is an attachment interface156 covering the bottom surface 149 and having an adhesive surface 157for securing the case 146 to the skin of a test subject. The interface156 defines a pair of apertures 159 disposed to receive the contacts151. Also defined by the interface 156 are a plurality of spaced apartopenings 161 juxtaposed to and in communication with the grooves 153.During use of the electrode 145, the grooves 153 and openings 161provide passages for escape of excess moisture and thereby prevent apremature failure of the adhesive on the surface 157 of the interface156.

Partially shown in FIGS. 19 and 20 is a modified attachment interface165 for use with the electrode 145 depicted in FIG. 18. Covering each ofthe apertures 159 of the interface 165 is a flexible container pad 166.Each pad 166 is formed by an array of transversely spaced apartrupturable capsules 168 filled with electrolytes. The capsules 168 areretained by a flexible fiber matrix 169. During attachment of theinterface 165 to the skin of a test subject, the capsules 168 arecrushed and rupture to release their electrolyte contents in the regionsbetween the skin and the contacts 151 and thereby enhance conductivitytherebetween.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is to be understood,therefore, that the invention can be practiced otherwise than asspecifically described.

What is claimed is:
 1. A biomedical electrode comprising: anon-conductive case having a top surface and a bottom surface forattachment to the skin; an adhesive substance covering a portion of saidbottom surface; a plurality of contacts retained by said case andprojecting outwardly from said bottom surface, each of said contactshaving an outer surface portion for contacting the skin; and whereinsaid bottom surface comprises a base portion inwardly displaced fromsaid outer surface portions and transition portions sloping between saidbase portion and each of said outer surface portions.
 2. A biomedicalelectrode according to claim 1 wherein each said outer surface portionis elongated with a pair of longitudinal edges at least one of which isintersected by one of said transition portions.
 3. A biomedicalelectrode according to claim 2 wherein said elongated surface portionsare arranged in a substantially parallel array disposed substantiallyparallel to said base portion.
 4. A biomedical electrode according toclaim 3 wherein each of said transition portions is concave.
 5. Abiomedical electrode according to claim 4 wherein each of saidtransition portions forms a catenary curve.
 6. A biomedical electrodeaccording to claim 3 wherein each of said contacts is cylindrical anddisposed substantially parallel to said base portion.
 7. A biomedicalelectrode according to claim 6 wherein each of said transition portionsis concave.
 8. A biomedical electrode according to claim 7 wherein eachof said transition portions forms a catenary curve.
 9. A biomedicalelectrode according to claim 2 wherein each of said edges is intersectedby one of said transition portions.
 10. A biomedical electrode accordingto claim 9 wherein said elongated surface portions are arranged in asubstantially parallel array disposed substantially parallel to saidbase portion.
 11. A biomedical electrode according to claim 10 whereineach of said transition portions is concave.
 12. A biomedical electrodeaccording to claim 11 wherein each of said transition portions forms acatenary curve.
 13. A biomedical electrode according to claim 9 whereineach of said contacts is cylindrical and disposed substantially parallelto said base portion.
 14. A biomedical electrode according to claim 10wherein said elongated surface portions are arranged in a substantiallyparallel array disposed substantially parallel to said base portion. 15.A biomedical electrode according to claim 9 wherein each of saidtransition portions is concave.
 16. A biomedical electrode according toclaim 12 wherein each of said transition portions forms a catenarycurve.
 17. A biomedical electrode according to claim 1 wherein each ofsaid transition portions is concave.
 18. A biomedical electrodeaccording to claim 14 wherein each of said transition portions forms acatenary curve.
 19. A biomedical electrode according to claim 15 whereineach of said contacts is cylindrical and disposed substantially parallelto said base portion.